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Set Data Structure

Started by GDKnight Feb 1, 2006 at 10:57 PM 0 replies 950+ views

Original Post

Feb 1, 2006 at 10:57 PM

I was wondering if anyone could explain this structure in more detail. Wikipedia has a brief summary of them. I just can't seem to understand why this is important. Why I would ever use this and when I would come across this? Why wouldn't I just store something in an array list or something why create a set? I guess I need to know also where would you use this, and how would it help in that situation.

nilkn

122

nilkn

Feb 1, 2006 at 11:07 PM

In my experience they aren't particularly useful.

The set structure is rather simple: an object simply is or is not in the set. Order does not play a part. A normal 'set' cannot contain duplicates (inserting the same object more than once won't change the set), and is therefore useful for culling out duplicates in another container. A 'multiset' will store equal objects as the name implies.

Some example uses (courtesy of "C++ for Game Programmers" by Noel Llopis, because I couldn't think of any myself [smile]):

- Keep a set of collision normals so you don't process the same one multiple times.
- Keep a set of objects that you are reading from disk. Those objects are read in date order (older to newer), and newer objects can override older ones. PUtting them in a set as we read them will automatically check whether they already existed and override the old ones.

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